Open Source Profilers in C#

Prof-It is an easy-to-use standalone profiler for C# that measures execution frequencies for each statement while keeping the instrumentation of the source code to a minimum.
An optimized strategy for finding basic blocks, incrementing their counters and calculating counters from others makes Prof-It faster than every other profiler, that can collect execution frequencies for each line of code!

SlimTune is a free profiler and performance analysis/tuning tool for .NET applications. It provides many powerful features, such as remote profiling, real time results, multiple plugin-based visualizations, and much more. The source code is available under the terms of the MIT License.